The objectives of these studies are to characterize the formation of pulmonary cysts that are composed of reaggregated pulmonary epithelium. These studies provide a technique to study the non-respiratory activities of terminal airway cells in an in vitro model system. In this system cell-to-cell interactions can be studied and the effects of a variety of agents including pollutants can be assessed with regard to lung cell function. The structure of these cell aggregates, or cysts, is to be studied by morphological and biochemical techniques in order to establish baseline parameters as compared with in situ lung. Other studies concerning the role of other cell types that interact with Type II cells are to be explored with regard to the maintenance of the structural and functional integrity of these pulmonary cysts.